Because the tires are the only points of contact between a vehicle and the road, tires are one of the most crucial safety components in the vehicle, for all types of vehicles, such as cars, trucks, sport utility vehicles, off-road vehicles, airplanes, motorcycles, bicycles, mobile industrial and construction equipment, and the like. Tires are responsible for how the vehicle responds to the driving and steering. To optimize the effects of the tires on the road and therefore, to provide for safety of the vehicle, the inflation pressure of tires must be kept within the manufacturer's prescribed range. Tires that are driven under-inflated generate excessively high heat levels that can weaken the tire to the point of failure. At high speed, a rapidly deflating tire can cause loss of vehicle control. An over-inflated tire will result in harsh ride quality and can cause uneven tire wear. Furthermore, operating a vehicle with over- or under-inflated tires increases both fuel consumption and the exhaust emissions produced by the vehicle.
Tires are designed to grip the road, allowing the vehicle to start, stop and go around corners safely in any weather. Proper treads allow for normal handling of a vehicle and help prevent skidding and hydroplaning. Treads wear out over time. As a consequence, the distance that is required to stop a vehicle increases with the wear of tires. A recent series of tests conducted for The British Rubber Manufacturers Association by MIRA has shown that the stopping distance significantly increases and cornering performance deteriorates when tire tread depth falls below 3 mm, even if the legal minimum tread depth is 1.6 mm (generally, tire tread depth is comprised between 7 and 9 mm). So, it is extremely important to check the tire treads for signs of wear as well as tire pressure.
It is known in the automotive industry to provide for wireless monitoring of vehicle tire parameters, particularly tire pressure. In such tire pressure monitoring systems, tire pressure sensors and radio frequency transmitters are mounted inside each tire, typically adjacent the inflation valve system. In each tire, the tire pressure sensed by the tire pressure sensor is transmitted by the transmitter to a receiver/controller localized on the vehicle. The tire pressure information delivered to the receiver/controller by the radio frequency signal from the transmitters is subsequently conveyed to a vehicle operator or occupant, typically in the form of a display.
When a single reader is used to monitor several tires such operation can create problems when tires are subsequently rotated or changed from their initial locations to new locations, or when a vehicle tire is replaced. Each time the vehicle tires are rotated or a tire is replaced, initialization or sign-up must be repeated to ensure that the system continues to operate properly by conveying accurate information, including tire location, to the vehicle operator. This initialization requirement makes tire rotation more complex, and increases the possibility of inaccurate operation of the system.
U.S. Pat. No. 6,788,193 discloses a system for remote control of tire pressure in a vehicle having front tires including a right tire and a left tire, and rear tires including a right tire and a left tire, and for automatically identifying tire location. A transmitter mounted in each tire transmits a tire information signal conveying tire pressure data and associated tire rotation direction data. A vehicle mounted receiver has a location a first distance from the front tires and a second distance from the rear tires, the first distance being different from the second. A vehicle mounted controller in communication with the receiver determines whether pressure data is associated with a front tire or a rear tire based on the strength of the tire information signal, and whether pressure data is associated with a right tire or a left tire based on the associated rotation direction data.
A particular problem associated with signal processing in vehicle environment lies in the metallic structure of the vehicle that generates signal reflection and perturbation. Measuring signal strength of a signal emitted by an emitter mounted inside a tire in rotation is complex and subject to many parameters that could lead to inaccurate operation of the system.
Thus, there exists a need for an improved system and method for identifying tire location without the need of an initialization step.